Declare them. If you don't know what the implications are of an error message you can always use diagnostics:

$ perl -Mstrict -Mdiagnostics -e '$x=1;'
Global symbol "$x" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors (#1)
    (F) You've said "use strict" or "use strict vars", which indicates
+ 
    that all variables must either be lexically scoped (using "my" or 
+"state"), 
    declared beforehand using "our", or explicitly qualified to say 
    which package the global variable is in (using "::").
    
Uncaught exception from user code:
        Global symbol "$x" requires explicit package name at -e line 1
+.
        Execution of -e aborted due to compilation errors.
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Thanks for the tool. I thought about that but i already declare my variable in my loop. I just want to recover them in this code part

 unless ($white{browser_name => $browser[0]}->compare($blue{browser_na
+me => $browser[1]})) {
    $diff_file = $white->difference($blue);
    print '#The images differ; see ' . $diff_file . ' for details'. "\
+n";
  

  my $open_cmd;
  if ($^O eq 'darwin') {
      $open_cmd = 'open'
  }
  elsif ($^O eq 'MSWin32') {
      $open_cmd = '';
  }
  else {
      $open_cmd = 'display';
  }
  `$open_cmd $diff_file`;
  }
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Lost in translation

but i already declare my variable in my loop

No, you don't. You have not declared $diff_file in any part of the code which you have shown.

unless ($white{browser_name => $browser[0]}->compare($blue{browser_name => $browser[1]})) {
   $diff_file = $white->difference($blue);
   print '#The images differ; see ' . $diff_file . ' for details'. "\n";
   ...
   }

I don't understand what you're trying to do with an expression like $white{browser_name => $browser[0]}, but I doubt it's the right way to go.

You're trying to use the old fashioned (pre-Perl 5) multidimensional array hack | emulation on the hash  %white which you have never declared. (Update: You're not accessing the  $white object reference.)

c:\@Work\Perl\monks>perl -wMstrict -le
"use Data::Dump qw(dd);
 ;;
 my %white;
 ;;
 my @bar = qw(bozzle);
 ;;
 $white{ foo => $bar[0] } = 'wibble';
 dd \%white;
"
{ "foo\34bozzle" => "wibble" }
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The  "foo\34bozzle" key in the dd dump is part of this old hack. See  $; in perlvar for some info on this. I'd like to give you a more complete reference, but I can't seem to find one ATM. (Anyone...?) (Update: Ok, there's this brief discussion on-line in perldata: Multi-dimensional array emulation.)

---

Give a man a fish:  <%-{-{-{-<

You use both $white-> and $white{...} (similarly for most of the other errors). The $white-> variant is using white as a scalar and the $white{...} variant is using white as a hash. You have either missed declaring the hash or, more likely, the second variant should be $white->{...}.

Because you haven't given enough context it is impossible for us to tell which way around the code should be.

The $diff_file error is fixed by prefixing the statement where it is assigned a value with my.

Oh ! It could be that, yes. I gave you all my sub . What does it miss for you ?
Lost in translation

I do not know Selenium, but my best guess is that the Selenium::Screenshot->new constructor invocation did not return a defined object. Check whether $white is defined right after that constructor invocation. It seems likely you might have a problem there.

Hello Laurent ! Concerning my constructor , it seems to work. When iam doing comparison within my loop , all is ok. Why i want to do comparison outside? Because i have to get all my browser' screenshots to be able to compare them. And my foreach return for each browser its screenshots. And if i want to compare 2 screenshots for 2 different browser, i think i have to do comparison outside loop.
Lost in translation

Then I have probably misunderstood your problem.

But you report this error:

Global symbol "%white" requires explicit package name at MyTest.pm lin
+e 33.
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And, in the code that you have shown, line 33 is within the loop.

If the code you show is not exactly the same as the one you run, it is difficult for us to figure out where exactly the error is occurring.

Looking at it again, the error seems to be in:

unless ($white{browser_name => $browser[0]} ...
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in which you use 'white' as a hash %white, not a scalar $white. Besides, $white has fallen out of scope anyway, so you would not be to access $white either, unless you had declared it before the start of the loop.

use parent 'Test::Class'; 
use Test::Selenium::Remote::Driver;
use Selenium::Screenshot;




my $url ="http://localhost;  


sub start : Test( start => no_plan ) {
  my $self = shift;
  $self->{browsers} = [('firefox', 'internet explorer', 'chrome', 'ope
+ra')];

}
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